As the power available in the initial phase of the ITER operation will be limited, accessing the high confinement mode （H-mode） with low heating power will be a critical issue. In the recent experiment on EAST, the ...As the power available in the initial phase of the ITER operation will be limited, accessing the high confinement mode （H-mode） with low heating power will be a critical issue. In the recent experiment on EAST, the H-mode was obtained for the first time with lower hybrid current drive （LHCD） wave only. Reciprocating Langmuir probe measurements at the outer midplane showed that the electron density ne and electron tempel：ature Te in the scrape-off layer （SOL） were significantly reduced in the ELM-free phase, resulting in the increase of lower-hybrid wave （LHW） reflection. It was found that the power loss Ploss was comparable during the L-H transition, by comparing the adjacent L-mode and H-mode discharge. The Da emission, Te and ne decreased rapidly in the time scale of about 1 ms, and the radial electric field Er turned positive in this process near the last closed flux surface. Multiple L-H-L transitions were observed during a single shot when the applied LHW power was marginal to the threshold. The floating potential （Vf） had negative spikes corresponding with the Da signal, and Er oscillation evolved into several intermittent negative spikes just before the L-H transition. In some shots, dithering was observed just before the L-H transition.展开更多
It is crucial to increase the total stored energy by realizing the transition from a low confinement （L-mode） state to a high confinement （H-mode） state in magnetic confinement fusion. The L-H transition process i...It is crucial to increase the total stored energy by realizing the transition from a low confinement （L-mode） state to a high confinement （H-mode） state in magnetic confinement fusion. The L-H transition process is simulated by using the predictive transport code based on Weiland＇s fluid model. Based on the equilibrium parameters obtained from equilibrium fitting （EFIT） in the experiment, the electron density ne, electron temperature Te, ion temperatures lq, ion poloidal Vp, and toroidal momenta Vt are simulated self-consistently. The L-H transition dynamic behaviors with the formation of the transport barriers of ion and electron temperatures, the electron density, and the ion toroidal momenta are analyzed. During the L-H transition, the strong poloidal flow shear in the edge transport barrier region is observed. The crashes of the electron and ion temperature pedestals are also observed during the L-H transition. The effects of the heating and particle sources on the L-H transition process are studied systematically, and the critical power threshold of the L-H transition is also found.展开更多
The essential role of zonal flow in the L-H transition and the suppression of turbulence have been studied with a long range correlation technique using Langmuir probe arrays in EAST tokamak.Two toroidally localized p...The essential role of zonal flow in the L-H transition and the suppression of turbulence have been studied with a long range correlation technique using Langmuir probe arrays in EAST tokamak.Two toroidally localized probe arrays are used to measure the zonal flow during L-H transition and H-L back transition.The energy ratio of the low frequency zonal flow to the total drift wave turbulence is calculated.During ELM-free H mode,the energy ratio is higher than that in L mode,which reveals the important role of zonal flows in regulating turbulence amplitude in L-H transition.展开更多
This paper reviews the current state of understanding of the L-H transition phenomenon in tokamak plasmas with a focus on two central issues： （a） the mechanism for turbulence quick suppression at the L-H transitio...This paper reviews the current state of understanding of the L-H transition phenomenon in tokamak plasmas with a focus on two central issues： （a） the mechanism for turbulence quick suppression at the L-H transition; （b） the mechanism for subsequent generation of sheared flow. We briefly review recent advances in the understanding of the fast suppression of edge turbulence across the L-H transition. We uncover a comprehensive physical picture of the L-H transition by piecing together a number of recent experimental observations and insights obtained from 1D and 2D simulation models. Different roles played by diamagnetic mean flow, neoclassical-driven mean flow, turbulence-driven mean flow, and turbulence-driven zonal flows are discussed and clarified. It is found that the L-H transition occurs spontaneously mediated by a shift in the radial wavenumber spectrum of edge turbulence, which provides a critical evidence for the theory of turbulence quench by the flow shear. Remaining questions and some key directions for future investigations are proposed.展开更多
On the Large Helical Device （LHD） where nested magnetic surfaces are surrounded by the ergodic field layer, edge transport barrier （ETB） was produced in neutral-beam-injection （NBI） heated plasmas through transi...On the Large Helical Device （LHD） where nested magnetic surfaces are surrounded by the ergodic field layer, edge transport barrier （ETB） was produced in neutral-beam-injection （NBI） heated plasmas through transition and non-transition processes. The former case is the ETB formation by L-Htransition, where characteristics of L-H transition observed in a tokamak plasma are clearly recognized. The confinement improvement is the modest （- 10%）, compared with the ISS95 international stellarator scaling. The threshold power for the transition is comparable or slightly lower than the ITER scaling law established by tokamaks and compact tori. The ETB is formed inside the ergodic field layer of the vacuum field. The ETB formation destabilizes edge coherent modes such as m/n = 1/1, 2/3 and 1/2, of which rational surfaces are in the magnetic hill. The formed ETB is partially and transiently destroyed by these coherent edge MHD modes and edge localized modes （ELMs） typically observed in Ha signals. The latter ETB is observed in a plasma with large reversed NBI-driven current more than 100 kA at Bt = 1 T. In these plasmas, the edge magnetic shear is enhanced by the current and the rotational transform in the core region is expected to be appreciably reduced. Thus reduced rotational transform in the plasma central region will enhance outward heat and particle fluxes toward ergodic edge layer. The ETB with steep electron temperature gradient up to - 5 keV/m is formed by blocking enhanced outward heat flux.展开更多
In this paper, a mechanism about the variability of the L-H transition power thresh- old PL-H is proposed which is based on the ion orbit losses. Only in the edge where there are enough ion orbit losses and the negati...In this paper, a mechanism about the variability of the L-H transition power thresh- old PL-H is proposed which is based on the ion orbit losses. Only in the edge where there are enough ion orbit losses and the negative radial electric field Er is high enough can the H-mode be triggered. The ion orbit losses are determined by the ion in the loss region under certain edge conditions. For different mass A and different charge Z, the critical loss energy E Z2/A in the loss region. In H and D charges, because the D＋ loss region is larger than H＋, it can be deduced that the PL-H of H is larger than that of D. In a 4He discharge, experiment finds there exist a considerable number of 4He1＋ in the plasma edge. The actual ion orbit losses are determined by the mixing ratio of a He1＋ and 4He2＋. The 4He1＋ loss region is larger than that of 4He2＋, and the loss region of D＋ interposes between 4He1＋ and 4He2＋. Different 4He1＋ content can cause the edge ion losses in a 4He discharge to be greater than, less than or equal to that in a D discharge. So a 4He discharge can exhibit multiple experimental phenomena in the PL-H.展开更多
Areversed phase liquid chromatographic method for determination of acetaminophen in human plasm andthe pharmacokinetics ofacetaminophen in humans were studied . The drug was extracted from human plasm with diethylethe...Areversed phase liquid chromatographic method for determination of acetaminophen in human plasm andthe pharmacokinetics ofacetaminophen in humans were studied . The drug was extracted from human plasm with diethylether . A C1 8 column (5 μm ,200 m m ×4 .6 m m ) accompaned with the mobil phase composed of methanol 0 .022 mol L Na Ac 0 .126 mol L H Ac (25 ∶50 ∶50) was used . Salicylic acid was used as internal standard and detectivewavelength was 233 nm . The calibration curves showed good linearity overthe range of 0 .112 μgml. The recoveries ofacetaminophen were 94 .3 % 101 .7 % for plasma . After a single dose of 500 mg of acetaminophen granula , theconcentration time curves conformed to one compartment model. Cm a x = (5 .94 ±0 .69) μgml , tm ax = (0 .73 ±0 .32)h ,t1 2 Ke = (2 .38 ±0 .85) h , t12 Ka = (0 .21 ±0 .14 ) h , A U C0 → ∞ = (25 .87 ±6 .73) μg·h ml .展开更多
The High Resolution Model Intercomparison Project(HighResMIP)is a unique model intercomparison project in phase 6 of the Coupled Model Intercomparison Project(CMIP6),which is focused on the impact of horizontal resolu...The High Resolution Model Intercomparison Project(HighResMIP)is a unique model intercomparison project in phase 6 of the Coupled Model Intercomparison Project(CMIP6),which is focused on the impact of horizontal resolutions.The outputs of the high-and low-resolution versions of CAS FGOALS-f3-H and CAS FGOALS-f3-L for the experiments of the HighResMIP simulations in CMIP6 are described in this paper.The models and their configurations,experimental settings,and postprocessing methods are all introduced.CAS FGOALS-f3-H,with a 0.25°horizontal resolution,and CAS FGOALS-f3-L,with a 1°horizontal resolution,were forced by the standard external conditions,and two coordinated sets of simulations were conducted for 1950–2014 and 2015–50 with the Experiment IDs of‘highresSST-present’and‘highresSST-future’,respectively.The model outputs contain multiple time scales including the required hourly mean,three-hourly mean,six-hourly transient,daily mean,and monthly mean datasets.It is reported that the 0.25°CAS FGOALS-f3-H successfully simulates some of the key challenges in climate modeling,including the average lifetime of tropical cyclones,particularly in the western parts of the northern Pacific Ocean,and the diurnal cycle of hourly precipitation.These datasets will contribute to the benchmarking of current models for CMIP,and studies of the impacts of horizontal resolutions on climate modeling issues.展开更多
基金supported by the National Magnetic Confinement Fusion Science Program of China (No. 2011GB107001)National Natural Science Foundation of China (Nos. 11075181, 10725523, 10721505, 10990212, 10605028)the ITER project of China (No. 2010GB104001)
文摘As the power available in the initial phase of the ITER operation will be limited, accessing the high confinement mode （H-mode） with low heating power will be a critical issue. In the recent experiment on EAST, the H-mode was obtained for the first time with lower hybrid current drive （LHCD） wave only. Reciprocating Langmuir probe measurements at the outer midplane showed that the electron density ne and electron tempel：ature Te in the scrape-off layer （SOL） were significantly reduced in the ELM-free phase, resulting in the increase of lower-hybrid wave （LHW） reflection. It was found that the power loss Ploss was comparable during the L-H transition, by comparing the adjacent L-mode and H-mode discharge. The Da emission, Te and ne decreased rapidly in the time scale of about 1 ms, and the radial electric field Er turned positive in this process near the last closed flux surface. Multiple L-H-L transitions were observed during a single shot when the applied LHW power was marginal to the threshold. The floating potential （Vf） had negative spikes corresponding with the Da signal, and Er oscillation evolved into several intermittent negative spikes just before the L-H transition. In some shots, dithering was observed just before the L-H transition.
基金supported by the Funds of the Youth Innovation Team of Science and Technology in Sichuan Province,China(Grant No.2014TD0023)the National Natural Science Foundation of China(Grant Nos.11447228 and 11205053)the China National Magnetic Confinement Fusion Science Program(Grant No.2013GB107001)
文摘It is crucial to increase the total stored energy by realizing the transition from a low confinement （L-mode） state to a high confinement （H-mode） state in magnetic confinement fusion. The L-H transition process is simulated by using the predictive transport code based on Weiland＇s fluid model. Based on the equilibrium parameters obtained from equilibrium fitting （EFIT） in the experiment, the electron density ne, electron temperature Te, ion temperatures lq, ion poloidal Vp, and toroidal momenta Vt are simulated self-consistently. The L-H transition dynamic behaviors with the formation of the transport barriers of ion and electron temperatures, the electron density, and the ion toroidal momenta are analyzed. During the L-H transition, the strong poloidal flow shear in the edge transport barrier region is observed. The crashes of the electron and ion temperature pedestals are also observed during the L-H transition. The effects of the heating and particle sources on the L-H transition process are studied systematically, and the critical power threshold of the L-H transition is also found.
基金the EAST team for their support during the experimentssupported by the National Natural Science Foundation of China with Grant Nos.10990210,10990211,11375188,11105144,and 11375053+1 种基金the National Magnetic Confinement Fusion Science Program of China under Contracts Nos.2013GB106002, 2013GB106003the Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology with Grant No.2014FXCX003
文摘The essential role of zonal flow in the L-H transition and the suppression of turbulence have been studied with a long range correlation technique using Langmuir probe arrays in EAST tokamak.Two toroidally localized probe arrays are used to measure the zonal flow during L-H transition and H-L back transition.The energy ratio of the low frequency zonal flow to the total drift wave turbulence is calculated.During ELM-free H mode,the energy ratio is higher than that in L mode,which reveals the important role of zonal flows in regulating turbulence amplitude in L-H transition.
文摘This paper reviews the current state of understanding of the L-H transition phenomenon in tokamak plasmas with a focus on two central issues： （a） the mechanism for turbulence quick suppression at the L-H transition; （b） the mechanism for subsequent generation of sheared flow. We briefly review recent advances in the understanding of the fast suppression of edge turbulence across the L-H transition. We uncover a comprehensive physical picture of the L-H transition by piecing together a number of recent experimental observations and insights obtained from 1D and 2D simulation models. Different roles played by diamagnetic mean flow, neoclassical-driven mean flow, turbulence-driven mean flow, and turbulence-driven zonal flows are discussed and clarified. It is found that the L-H transition occurs spontaneously mediated by a shift in the radial wavenumber spectrum of edge turbulence, which provides a critical evidence for the theory of turbulence quench by the flow shear. Remaining questions and some key directions for future investigations are proposed.
基金supported in part by the JSPS-CAS Core-University Program in the field of Plasma and Nuclear Fusion and the JSPS Grant-in-Aid for Exploratory Research(No.6656287)
文摘On the Large Helical Device （LHD） where nested magnetic surfaces are surrounded by the ergodic field layer, edge transport barrier （ETB） was produced in neutral-beam-injection （NBI） heated plasmas through transition and non-transition processes. The former case is the ETB formation by L-Htransition, where characteristics of L-H transition observed in a tokamak plasma are clearly recognized. The confinement improvement is the modest （- 10%）, compared with the ISS95 international stellarator scaling. The threshold power for the transition is comparable or slightly lower than the ITER scaling law established by tokamaks and compact tori. The ETB is formed inside the ergodic field layer of the vacuum field. The ETB formation destabilizes edge coherent modes such as m/n = 1/1, 2/3 and 1/2, of which rational surfaces are in the magnetic hill. The formed ETB is partially and transiently destroyed by these coherent edge MHD modes and edge localized modes （ELMs） typically observed in Ha signals. The latter ETB is observed in a plasma with large reversed NBI-driven current more than 100 kA at Bt = 1 T. In these plasmas, the edge magnetic shear is enhanced by the current and the rotational transform in the core region is expected to be appreciably reduced. Thus reduced rotational transform in the plasma central region will enhance outward heat and particle fluxes toward ergodic edge layer. The ETB with steep electron temperature gradient up to - 5 keV/m is formed by blocking enhanced outward heat flux.
基金supported by National Natural Science Foundation of China(No.11175210)
文摘In this paper, a mechanism about the variability of the L-H transition power thresh- old PL-H is proposed which is based on the ion orbit losses. Only in the edge where there are enough ion orbit losses and the negative radial electric field Er is high enough can the H-mode be triggered. The ion orbit losses are determined by the ion in the loss region under certain edge conditions. For different mass A and different charge Z, the critical loss energy E Z2/A in the loss region. In H and D charges, because the D＋ loss region is larger than H＋, it can be deduced that the PL-H of H is larger than that of D. In a 4He discharge, experiment finds there exist a considerable number of 4He1＋ in the plasma edge. The actual ion orbit losses are determined by the mixing ratio of a He1＋ and 4He2＋. The 4He1＋ loss region is larger than that of 4He2＋, and the loss region of D＋ interposes between 4He1＋ and 4He2＋. Different 4He1＋ content can cause the edge ion losses in a 4He discharge to be greater than, less than or equal to that in a D discharge. So a 4He discharge can exhibit multiple experimental phenomena in the PL-H.
文摘Areversed phase liquid chromatographic method for determination of acetaminophen in human plasm andthe pharmacokinetics ofacetaminophen in humans were studied . The drug was extracted from human plasm with diethylether . A C1 8 column (5 μm ,200 m m ×4 .6 m m ) accompaned with the mobil phase composed of methanol 0 .022 mol L Na Ac 0 .126 mol L H Ac (25 ∶50 ∶50) was used . Salicylic acid was used as internal standard and detectivewavelength was 233 nm . The calibration curves showed good linearity overthe range of 0 .112 μgml. The recoveries ofacetaminophen were 94 .3 % 101 .7 % for plasma . After a single dose of 500 mg of acetaminophen granula , theconcentration time curves conformed to one compartment model. Cm a x = (5 .94 ±0 .69) μgml , tm ax = (0 .73 ±0 .32)h ,t1 2 Ke = (2 .38 ±0 .85) h , t12 Ka = (0 .21 ±0 .14 ) h , A U C0 → ∞ = (25 .87 ±6 .73) μg·h ml .
基金jointly funded by the Strategic Priority Research Program of Chinese Academy of Sciences grant number XDB40030205the National Natural Science Foundation of China grant numbers 91737306,41675100,and U1811464。
文摘The High Resolution Model Intercomparison Project(HighResMIP)is a unique model intercomparison project in phase 6 of the Coupled Model Intercomparison Project(CMIP6),which is focused on the impact of horizontal resolutions.The outputs of the high-and low-resolution versions of CAS FGOALS-f3-H and CAS FGOALS-f3-L for the experiments of the HighResMIP simulations in CMIP6 are described in this paper.The models and their configurations,experimental settings,and postprocessing methods are all introduced.CAS FGOALS-f3-H,with a 0.25°horizontal resolution,and CAS FGOALS-f3-L,with a 1°horizontal resolution,were forced by the standard external conditions,and two coordinated sets of simulations were conducted for 1950–2014 and 2015–50 with the Experiment IDs of‘highresSST-present’and‘highresSST-future’,respectively.The model outputs contain multiple time scales including the required hourly mean,three-hourly mean,six-hourly transient,daily mean,and monthly mean datasets.It is reported that the 0.25°CAS FGOALS-f3-H successfully simulates some of the key challenges in climate modeling,including the average lifetime of tropical cyclones,particularly in the western parts of the northern Pacific Ocean,and the diurnal cycle of hourly precipitation.These datasets will contribute to the benchmarking of current models for CMIP,and studies of the impacts of horizontal resolutions on climate modeling issues.
